Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2 2/7] KVM: x86: Add helpers to perform CPUID-based guest vendor check | From | Xiaoyao Li <> | Date | Thu, 5 Mar 2020 11:48:20 +0800 |
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On 3/5/2020 9:34 AM, Sean Christopherson wrote: > Add helpers to provide CPUID-based guest vendor checks, i.e. to do the > ugly register comparisons. Use the new helpers to check for an AMD > guest vendor in guest_cpuid_is_amd() as well as in the existing emulator > flows. > > Using the new helpers fixes a _very_ theoretical bug where > guest_cpuid_is_amd() would get a false positive on a non-AMD virtual CPU > with a vendor string beginning with "Auth" due to the previous logic > only checking EBX. It also fixes a marginally less theoretically bug > where guest_cpuid_is_amd() would incorrectly return false for a guest > CPU with "AMDisbetter!" as its vendor string. > > Fixes: a0c0feb57992c ("KVM: x86: reserve bit 8 of non-leaf PDPEs and PML4Es in 64-bit mode on AMD") > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > --- > arch/x86/include/asm/kvm_emulate.h | 24 ++++++++++++++++++++ > arch/x86/kvm/cpuid.h | 2 +- > arch/x86/kvm/emulate.c | 36 +++++++----------------------- > 3 files changed, 33 insertions(+), 29 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h > index bf5f5e476f65..2754972c36e6 100644 > --- a/arch/x86/include/asm/kvm_emulate.h > +++ b/arch/x86/include/asm/kvm_emulate.h > @@ -393,6 +393,30 @@ struct x86_emulate_ctxt { > #define X86EMUL_CPUID_VENDOR_GenuineIntel_ecx 0x6c65746e > #define X86EMUL_CPUID_VENDOR_GenuineIntel_edx 0x49656e69 > > +static inline bool is_guest_vendor_intel(u32 ebx, u32 ecx, u32 edx) > +{ > + return ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx && > + ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx && > + edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx; > +} > + > +static inline bool is_guest_vendor_amd(u32 ebx, u32 ecx, u32 edx) > +{ > + return (ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx && > + ecx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx && > + edx == X86EMUL_CPUID_VENDOR_AuthenticAMD_edx) || > + (ebx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ebx && > + ecx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ecx && > + edx == X86EMUL_CPUID_VENDOR_AMDisbetterI_edx); > +} > + > +static inline bool is_guest_vendor_hygon(u32 ebx, u32 ecx, u32 edx) > +{ > + return ebx == X86EMUL_CPUID_VENDOR_HygonGenuine_ebx && > + ecx == X86EMUL_CPUID_VENDOR_HygonGenuine_ecx && > + edx == X86EMUL_CPUID_VENDOR_HygonGenuine_edx; > +} > +
Why not define those in cpuid.h ? And also move X86EMUL_CPUID_VENDOR_* to cpuid.h and remove the "EMUL" prefix.
> enum x86_intercept_stage { > X86_ICTP_NONE = 0, /* Allow zero-init to not match anything */ > X86_ICPT_PRE_EXCEPT, > diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h > index 7366c618aa04..13eb3e92c6a9 100644 > --- a/arch/x86/kvm/cpuid.h > +++ b/arch/x86/kvm/cpuid.h > @@ -145,7 +145,7 @@ static inline bool guest_cpuid_is_amd(struct kvm_vcpu *vcpu) > struct kvm_cpuid_entry2 *best; > > best = kvm_find_cpuid_entry(vcpu, 0, 0); > - return best && best->ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx; > + return best && is_guest_vendor_amd(best->ebx, best->ecx, best->edx); > } > > static inline int guest_cpuid_family(struct kvm_vcpu *vcpu) > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index dd19fb3539e0..9cf303984fe5 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -2712,9 +2712,7 @@ static bool vendor_intel(struct x86_emulate_ctxt *ctxt) > > eax = ecx = 0; > ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false); > - return ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx > - && ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx > - && edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx; > + return is_guest_vendor_intel(ebx, ecx, edx); > } > > static bool em_syscall_is_enabled(struct x86_emulate_ctxt *ctxt) > @@ -2733,34 +2731,16 @@ static bool em_syscall_is_enabled(struct x86_emulate_ctxt *ctxt) > ecx = 0x00000000; > ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false); > /* > - * Intel ("GenuineIntel") > - * remark: Intel CPUs only support "syscall" in 64bit > - * longmode. Also an 64bit guest with a > - * 32bit compat-app running will #UD !! While this > - * behaviour can be fixed (by emulating) into AMD > - * response - CPUs of AMD can't behave like Intel. > + * remark: Intel CPUs only support "syscall" in 64bit longmode. Also a > + * 64bit guest with a 32bit compat-app running will #UD !! While this > + * behaviour can be fixed (by emulating) into AMD response - CPUs of > + * AMD can't behave like Intel. > */ > - if (ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx && > - ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx && > - edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx) > + if (is_guest_vendor_intel(ebx, ecx, edx)) > return false; > > - /* AMD ("AuthenticAMD") */ > - if (ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx && > - ecx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx && > - edx == X86EMUL_CPUID_VENDOR_AuthenticAMD_edx) > - return true; > - > - /* AMD ("AMDisbetter!") */ > - if (ebx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ebx && > - ecx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ecx && > - edx == X86EMUL_CPUID_VENDOR_AMDisbetterI_edx) > - return true; > - > - /* Hygon ("HygonGenuine") */ > - if (ebx == X86EMUL_CPUID_VENDOR_HygonGenuine_ebx && > - ecx == X86EMUL_CPUID_VENDOR_HygonGenuine_ecx && > - edx == X86EMUL_CPUID_VENDOR_HygonGenuine_edx) > + if (is_guest_vendor_amd(ebx, ecx, edx) || > + is_guest_vendor_hygon(ebx, ecx, edx)) > return true; > > /* >
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